JP2008031202A - Higher order silane compound and method for forming thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a uniform germanium-doped silicon conductive film on a substrate by a coating method under ordinary pressure, and to provide a method for producing a phosphorus atom-containing higher order silane compound therefor. <P>SOLUTION: A method for producing a germanium atom-containing higher order silane compound comprises irradiating a solution containing a photopolymerizable silane compound and a germanium compound with a ray having a longer wavelength than 400 nm to form the germanium atom-containing higher order silane compound. A method for forming a germanium-containing silicon film comprises coating the solution containing the germanium atom-containing higher order silane compound obtained by the above method on a substrate and heat-treating the coated substrate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a germanium silicon atom-containing high-order silicon compound that can be formed by a coating method and a method for forming a germanium-doped silicon film. More particularly, the present invention relates to a method for easily forming a high-quality silicon film that is applied to applications such as an integrated circuit, a thin film transistor, a photoelectric conversion device, and a photoreceptor.

  As a method for manufacturing silicon for semiconductors applied to integrated circuits, thin film transistors, and the like, a pulling method such as a CZ method or an FZ method, a vacuum process such as a CVD (Chemical Vapor Deposition) method, or the like can be given. In such a method, a silicon film is generally formed by a process of forming a silicon film on the entire surface and then removing unnecessary portions by photolithography. However, these methods have problems such as requiring a large-scale device, poor use efficiency of the raw material, difficulty in handling because the raw material is a gas, and generation of a large amount of waste.

Thin semiconductor layers are used in various electronic devices. For example, various quantum wells and superlattice structures have been used in photoelectron transfer transistors (HEMTs), laser diodes, light emitting diodes, and photodetectors. Such structures have been produced by well-known lattice matching and epitaxial techniques.
Amorphous and polycrystalline semiconductors are used in thin film transistors (TFTs), but a process for forming a uniform thin film of a uniform germanium-doped silicon film on a substrate by a coating method under normal pressure has not yet been completed.
On the other hand, in recent years, high-speed and large-capacity information devices and mobile devices have been promoted, and high-speed and low-power consumption MOS transistors are desired. Until now, characteristics have been improved by miniaturization of elements, but it is expected that element miniaturization will reach the limit in the near future. In view of this, attention has been paid to a technique for increasing the mobility of electrons and holes by using silicon or silicon germanium having a strained channel region so as to achieve high speed and low power consumption.

  An object of the present invention is to provide a method for producing a germanium atom-containing higher order silane compound by light irradiation from a photopolymerizable silane compound and a germanium compound.

  Another object of the present invention is to provide a uniform germanium phosphorus-doped silicon conductive material on a substrate by a coating method under normal pressure, which is a simple method, without using a deposition method from a gas phase that requires a large dedicated device. It is to provide a method of forming a film.

  Another object of the present invention is to use a germanium-doped silicon film obtained by this method as a silicon film for electronic devices.

  Still another object of the present invention is to provide a germanium-containing silane compound suitably used in the above-described method of the present invention.

  Still other objects and advantages of the present invention will become apparent from the following description.

According to the present invention, the above objects and advantages of the present invention are as follows.
Following formula (1)
Si _i H _{2i + 2} (1)
(Where i is an integer of 2 to 10), a chain silane compound represented by the following formula (2) or (2 ′)
Si _j H _2j (2)
Si _j H _2j-2 (2 ')
(Where j is an integer of 3 to 10) and the cyclic silane compound represented by the following formula (3)
Si _k H _k (3)
(Wherein k is 6, 8 or 10), a solution containing at least one liquid photopolymerizable silane compound and germanium compound selected from the group consisting of cage silane compounds This is achieved by a method for producing a germanium atom-containing higher order silane compound, characterized in that a germanium atom-containing higher order silane compound is produced by irradiation with light having a longer wavelength.

According to the present invention, the above objects and advantages of the present invention are secondly,
It is achieved by a method for forming a germanium-containing silicon film characterized by comprising a step of applying a solution containing a germanium atom-containing higher order silane compound obtained by the method of the present invention to a substrate and a step of heat-treating the coated substrate. The

According to the present invention, the above objects and advantages of the present invention are thirdly,
Higher order silane compounds produced by irradiating the silane compound represented by each of the above formulas (1), (2), (2 ′) and (3) with light having a wavelength longer than 400 nm, and the above formula (4) or It is achieved by a method for forming a germanium-containing silicon film, characterized by comprising a step of preparing a solution containing a germanium compound represented by (5), a step of applying this solution to a substrate, and a step of heat-treating the coated substrate. .

  According to the present invention, there is provided a method for forming a uniform germanium-doped silicon conductive film on a substrate by a coating method under normal pressure.

The photopolymerizable silane compound used in the method for producing a germanium atom-containing higher order silane compound of the present invention includes a chain silane compound represented by the above formula (1), a cyclic silane compound represented by the above formula (2), and the above formula. It is a cage silane compound represented by (3). These photopolymerizable silane compounds can be used alone or in combination of two or more.
Specific examples of such a photopolymerizable silane compound include disilane, trisilane, pentasilane, hexasilane, heptasilane, octasilane, nonasilane, and decasilane as the chain silane compound represented by the formula (1).

  As what has one cyclic structure represented by Formula (2), cyclotrisilane, cyclotetrasilane, cyclopentasilane, cyclohexasilane, cycloheptasilane etc. are mentioned, for example. As those having two cyclic structures represented by the formula (2 ′), for example, bicyclo [1.1.0] butasilane, bicyclo [2.1.0] pentasilane, bicyclo [2.2.0] hexasilane, Bicyclohe [3.2.0] Putasilane, Bicyclo [3.3.0] octasilane, Bicyclo [4.3.0] Nonasilane, Bicyclo [4.4.0] Decasilane, Spiro [2.2] pentasilane, Spiro [ 4.5] Decasilane, spiro [4.6] undecasilane, spiro [5.6] dodecasilane and the like.

  Further, examples of the cage silane compound represented by the formula (3) include the following compounds.

Further, silane compounds in which hydrogen atoms of these skeletons are partially substituted with SiH ₃ groups or halogen atoms such as fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, and the like can be given. These may be used in combination of two or more.
Among these, a silane compound having at least one cyclic structure in the molecule is preferably used because it has extremely high reactivity with light and can efficiently perform photopolymerization. Among them, cyclotetrasilane, cyclopentasilane, cyclohexasilane, and cycloheptasilane are particularly preferable because they can be easily synthesized and purified in addition to the above reasons.

The germanium compound used in the present invention is represented by the above formula (4) or (5). In the formulas (4) and (5), the R hydrocarbon group is preferably an alkyl group, an alkenyl group, an aryl group, or the like. Examples of R include methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, n-pentyl, phenyl, cyclopentadienyl, and fluorenyl. .
Examples of the germanium compound represented by the formula (5) or (6) include tert-butylgermanium, diethylgermane, di-n-butylgermane, diphenylgermane, trimethylgermane, triethylgermane, and tri-n-butylgermane. , Triphenylgermane, cyclopentadienyltrimethylgermane, phenyltrimethylgermane, fluorenyltrimethylgermane, diphenyldimethylgermane, hexamethyldigermane, hexaphenyldigermane, tetramethylgermane, tetraethylgermane, tetra-n-propylgermane, Tetra-n-butylgermane, tetrapentylgermane, tetraphenylgermane, tetra-p-tolylgermane, tris (trimethylsilyl) germane, germanium (powder) It can be mentioned.
The method of the present invention is carried out by dissolving a photopolymerizable silane compound and a germanium compound in a solvent-free or organic solvent as described above, and irradiating light having a wavelength longer than 300 nm, preferably 350 nm or more, particularly preferably. Is achieved by irradiating light of 400 nm or more.

  Specific examples of the organic solvent used in the silane compound solution include n-hexane, n-heptane, n-octane, n-decane, dicyclopentane, benzene, toluene, xylene, durene, indene, tetrahydronaphthalene, decahydro. Hydrocarbon solvents such as naphthalene, squalane, cyclohexane, cyclooctane, cyclodecane, dicyclohexyl, tetrahydrodicyclopentadiene, perhydrofluorene, tetradecahydroanthracene; dipropyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol methyl ethyl ether , Diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, tetrahydro Ether solvents such as lan, tetrahydropyran, 1,2-dimethoxyethane, bis (2-methoxyethyl) ether, p-dioxane; further propylene carbonate, γ-butyrolactone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, Mention may be made of polar solvents such as dimethyl sulfoxide. Among these, a hydrocarbon solvent and an ether solvent are preferable in view of solubility of the silane compound and stability of the solution, and a hydrocarbon solvent is particularly preferable. These solvents can be used singly or as a mixture of two or more.

The solution for light irradiation preferably contains 0.01 to 1000 parts by weight, more preferably 0.1 to 100 parts by weight of the germanium compound per 100 parts by weight of the photopolymerizable silane compound.
The organic solvent is preferably used in an amount of 10,000 parts by weight or less, more preferably 1,000 parts by weight or less, per 100 parts by weight of the total of the photopolymerizable silane compound and germanium compound.
The light irradiation is preferably performed in a non-oxidizing atmosphere such as nitrogen or argon.
The temperature of the solution during light irradiation is preferably 0 to 100 ° C., and the irradiation time can be, for example, 1 minute to 3 hours, preferably 5 minutes to 1 hour.
The light irradiation is performed with light having a wavelength longer than 300 nm.
For light irradiation, for example, an ultrahigh pressure mercury lamp of 200 to 750 W is preferably used. The irradiation energy can be, for example 10~10,000mW / cm ^2, preferably to a 500~6,000mW / cm ^2.
The germanium atom-containing higher order silane compound produced by light irradiation can be converted into a germanium-containing silicon film by a method in which the germanium atom-containing higher order silane compound is dissolved in an organic solvent and applied to a substrate, and the obtained coated substrate is heat-treated.

Thus, in the case of forming a silicon film, the process of irradiating light after mixing a germanium compound as a dopant source into the silane compound is a novel process that cannot be seen in the conventional method. According to such a process, irradiation with light can cause bonding between a dopant and a silane polymer at a molecular level. An n-type doped silicon film with good performance can be formed by applying the solution to the substrate and heat-treating it.
The coating solution preferably contains a phosphorus-containing silane compound at a concentration of 0.001 to 10% by weight. The coating thickness is such that the resulting germanium-containing silicon film is preferably 1 to 5,000 nm, more preferably 5 to 500 nm.
The heat treatment of the coating is preferably performed at 20 to 600 ° C, more preferably 100 to 500 ° C. The atmosphere of the heat treatment is preferably oxygen concentration: 10 ppm or less, moisture concentration: 10 ppm or less, more preferably oxygen concentration: 1 ppm or less, moisture concentration: 1 ppm or less, and the heat treatment time is, for example, 1 minute to 12 hours, preferably Although it is 5 minutes to 2 hours, it is desirable to set the heat treatment time according to the heating temperature.

Alternatively, according to the present invention, as a method for forming a silicon film, at least one silane compound represented by each of the formulas (1), (2), (2 ′) and (3) is more than 300 nm. A step of preparing a solution containing a high-order silane compound produced by irradiation with light having a long wavelength and a germanium compound represented by the formula (4) or (5), a step of applying the solution to a substrate, and the coated substrate; A method comprising the step of heat treating is provided.
The method for producing the higher order silane compound can be carried out in the same manner as the method for producing the germanium atom-containing higher order silane compound except that no germanium compound is used.
The use ratio of the higher order silane compound and the germanium compound represented by the formula (4) or (5) is such that the germanium compound is preferably 0.01 to 1000 parts by weight, more preferably 100 parts by weight of the higher order silane compound. Is 0.1 to 100 parts by weight.
As the solvent used in the step of preparing a solution containing these compounds, the same solvent as the organic solvent can be used. Both the step of applying the solution and the step of heat-treating the coated substrate can be performed in the same manner as in the forming method of the present invention.

The doped silicon film formed by the two methods can be further improved in characteristics by a step such as heating.
Further, the concentration of the dopant source to be added may be determined according to the finally required dopant concentration in the silicon film, and may be adjusted by diluting with a solvent after irradiation with light.
According to the germanium atom-containing higher order silane compound (polymer) of the present invention, a high-quality silicon film can be easily formed by the above effects as compared with the conventional method. The amorphous silicon film formed in this way can be crystallized by a method such as further heat treatment or excimer laser annealing to further improve the performance.

  Hereinafter, the present invention will be described in further detail with reference to examples. The present invention is not limited in any way by the examples.

Synthesis example 1
After replacing the inside of a 3 L four-necked flask equipped with a thermometer, a cooling condenser, a dropping funnel and a stirring device with argon gas, 1 L of dried tetrahydrofuran and 18.3 g of lithium metal were charged and bubbled with argon gas. . While this suspension was stirred at 0 ° C., 333 g of diphenyldichlorosilane was added from a dropping funnel, and after completion of the dropping, stirring was further continued for 12 hours at room temperature until the lithium metal completely disappeared. The reaction mixture was poured into 5 L of ice water to precipitate the reaction product. This precipitate was separated by filtration, washed well with water, then washed with cyclohexane, vacuum dried, and recrystallized with ethyl acetate to obtain 150 g of a white solid.

150 g of the obtained white solid and 500 ml of dried cyclohexane were charged into a 1 L flask, 20 g of aluminum chloride was added, and dry hydrogen chloride gas was bubbled for 10 hours while stirring while maintaining the reaction temperature at 30 ° C. Separately, 50 g of lithium aluminum hydride and 150 ml of diethyl ether were charged into a 1 L flask, the above reaction mixture was added with stirring at 0 ° C. in a nitrogen atmosphere, stirred at the same temperature for 1 hour, and further at room temperature for 12 hours. Stirring was continued. The reaction solution was suction filtered, and further by-products were removed from the filtrate, followed by distillation under reduced pressure at 70 ° C. and 10 mmHg. As a result, 10 g of a colorless liquid was obtained. This was found to be cyclopentasilane from the IR, ¹ H-NMR, ²⁹ Si-NMR, and GC-MS spectra.

Example 1
In a nitrogen stream (oxygen concentration: 0.1 ppm), 0.9 ml of cyclopentasilane and 0.1 ml of tert-butylgermanium were placed in a borosilicate glass sample tube, stirred, and a 750 W ultra-high pressure mercury lamp (UL750, manufactured by HOYA Candeo Optronics). ) Emitted from 405 nm (1,500 mW / cm ² ) for 50 minutes to obtain cyclopentasilane-germanium photopolymer (I).
On the other hand, in a nitrogen stream (oxygen concentration 0.1 ppm), 1.0 ml of cyclopentasilane is put into a sample tube made of borosilicate glass, stirred, and 405 nm light emitted from a 200 W ultra high pressure mercury lamp (Execule 3000 manufactured by HOYA Candeo Optronics). (100 mW / cm ² ) was irradiated for 10 minutes to obtain cyclopentasilane photopolymer (II).

The cyclopentasilane-germanium photopolymer (I) and cyclopentasilane photopolymer (II) obtained here were dissolved in d-toluene, and ¹ H-NMR and ²⁹ Si-NMR were measured.
In the ¹ H-NMR spectrum of the cyclopentasilane photopolymer (II), a broad peak believed to be derived from SiH ₂ or SiH ₃ was observed in the region of 2.8 to 3.8 ppm. On the other hand, the ¹ H-NMR spectrum of the cyclopentasilane-germanium photopolymer (I) seems to be derived from SiH ₂ or SiH ₃ and GeH ₃ , GeH ₂ , GeH _{1 in} the region of 2.8 to 3.8 ppm. A broad peak and a peak believed to be derived from tert-Bu were observed at 0.7 ppm.

In the ²⁹ Si-NMR spectrum of the cyclopentasilane photopolymer (II), a triplet peak believed to be derived from SiH ₂ was observed at −98 ppm, and a quartet peak believed to be derived from SiH ₃ was observed at −93 ppm. . On the other hand, the ²⁹ Si-NMR spectrum of the cyclopentasilane-germanium photopolymer (I) shows a multiplet peak that appears to be derived from SiH ₂ near −98 ppm and a multiplet that appears to be derived from SiH _{3 at} −93 ppm. A peak was observed.
From the above measurement results, the cyclopentasilane-germanium photopolymer (I) has a different structure from the cyclopentasilane photopolymer (II) obtained by polymerizing cyclopentasilane alone, that is, cyclopentasilane- Presumed to be a germanium compound.

Example 2
Next, cyclopentasilane-germanium photopolymer (I) was dissolved in t-decalin to prepare a 20% -cyclopentasilane-germanium photopolymer t-decalin solution (1).
In a nitrogen stream (oxygen concentration: 0.1 ppm), a 20% -cyclopentasilane-germanium photopolymer t-decalin solution (1) is spin-coated at a rotational speed of 2,000 rpm on a borosilicate glass substrate, and then at 540 ° C. It heated for 1 hour and obtained the sample board | substrate (A) and (silicon film thickness 60nm).
When the elemental composition ratio of the sample substrate (A) was determined from ESCA, the composition ratio of Si and Ge was 93: 7 on the film surface, 94: 6 when etched about 25 nm, and 94: 6 when etched about 50 nm. The obtained film was a silicon-germanium mixed film containing silicon and germanium.

Example 3
Cyclopentasilane-germanium photopolymer (I) 0.1 ml and cyclopentasilane photopolymer (II) 0.9 ml are mixed to prepare cyclopentasilane-germanium photopolymer (I): cyclopentasilane light. A mixture of polymer (II) = 1: 9 was prepared and then dissolved in t-decalin to prepare a 20% -cyclopentasilane-germanium photopolymer t-decalin solution (2).
In a nitrogen stream (oxygen concentration: 0.1 ppm), a 20% -cyclopentasilane-germanium photopolymer t-decalin solution (2) is spin-coated at a rotational speed of 2,000 rpm on a borosilicate glass substrate, and then at 540 ° C. It heated for 1 hour and obtained the sample board | substrate (B) and (silicon film thickness 65nm).
When the elemental composition ratio of the sample substrate (B) was obtained from ESCA, the composition ratio of Si and Ge was 99.2: 0.8 on the film surface and 99.3: 0.7, about 50 nm when etched about 25 nm. When etched, it was 99.3: 0.7, and the obtained film was a silicon-germanium mixed film containing silicon and germanium.

Example 4
In a nitrogen stream (oxygen concentration: 0.1 ppm), 0.5 ml of cyclopentasilane and 0.5 ml of tert-butylgermanium were placed in a borosilicate glass sample tube, stirred, and a 750 W ultra high pressure mercury lamp (HOYA Candeo Optronics Co., Ltd.). Manufactured by UL750) was irradiated with 405 nm light (6,000 mW / cm ² ) for 50 minutes to obtain a cyclopentasilane-germanium photopolymer (III).
Next, cyclopentasilane-germanium photopolymer (III) was dissolved in t-decalin to prepare a 20% -cyclopentasilane-germanium photopolymer t-decalin solution (3).
A 20% -cyclopentasilane-germanium photopolymer t-decalin solution (3) is spin-coated at a rotational speed of 2,000 rpm on a borosilicate glass substrate in a nitrogen stream (oxygen concentration 0.1 ppm), and then at 540 ° C. Heated for 1 hour to obtain a sample substrate (C) (film thickness 50 nm).
When the elemental composition ratio of the sample substrate (C) was obtained from ESCA, the composition ratio of Si and Ge was 57:43 on the film surface, and 55:45 was obtained when the film was etched about 25 nm. It was shown to be a silicon-germanium mixed film containing germanium.

Example 5
In a nitrogen stream (oxygen concentration 0.1 ppm), 0.2 ml of cyclopentasilane and 0.8 ml of tert-butylgermanium were placed in a borosilicate glass sample tube and stirred, and a 750 W ultra-high pressure mercury lamp (HOYA Candeo Optronics Co., Ltd. UL750) ) Emitted from 405 nm light (7,500 mW / cm ² ) for 50 minutes to obtain cyclopentasilane-germanium photopolymer (IV).
Next, cyclopentasilane-germanium photopolymer (IV) was dissolved in t-decalin to prepare a 20% -cyclopentasilane-germanium photopolymer t-decalin solution (4).
In a nitrogen stream (oxygen concentration: 0.1 ppm), a 20% -cyclopentasilane-germanium photopolymer t-decalin solution (4) is spin-coated at 2,000 rpm on a borosilicate glass substrate, and then at 540 ° C. It heated for 1 hour and obtained the sample board | substrate (D) and (film thickness 45nm).
When the elemental composition ratio of the sample substrate (D) was obtained from ESCA, the composition ratio of Si and Ge was 22:78 on the film surface, and 20:80 was obtained after etching at about 20 nm. It was shown to be a silicon-germanium mixed film containing germanium.

Example 6
In a nitrogen stream (oxygen concentration 0.1 ppm), 0.1 ml of cyclopentasilane and 0.9 ml of tert-butylgermanium were placed in a sample tube made of borosilicate glass and stirred, and a 750 W ultra-high pressure mercury lamp (HOYA Candeo Optronics Co., Ltd. UL750) ) Emitted from 405 nm (7,500 mW / cm ² ) for 60 minutes to obtain a cyclopentasilane-germanium photopolymer (V).
Next, cyclopentasilane-germanium photopolymer (V) was dissolved in t-decalin to prepare a 20% -cyclopentasilane-germanium photopolymer t-decalin solution (5).
A 20% -cyclopentasilane-germanium photopolymer t-decalin solution (5) is spin-coated at a rotational speed of 2,000 rpm on a borosilicate glass substrate in a nitrogen stream (oxygen concentration 0.1 ppm), and then at 540 ° C. It heated for 1 hour and obtained the sample board | substrate (E) (film thickness of 40 nm).
When the elemental composition ratio of the sample substrate (E) was determined from ESCA, the composition ratio of Si and Ge was 11:89 on the film surface, and 9:91 was obtained when the film was etched by about 20 nm. It was shown to be a silicon-germanium mixed film containing germanium.

Claims (4)

Following formula (1)
Si _i H _{2i + 2} (1)
(Where i is an integer of 2 to 10), a chain silane compound represented by the following formula (2) or (2 ′)
Si _j H _2j (2)
Si _j H _2j-2 (2 ')
(Where j is an integer of 3 to 10) and the cyclic silane compound represented by the following formula (3)
Si _k H _k (3)
(Wherein k is 6, 8 or 10), a solution containing at least one liquid photopolymerizable silane compound and germanium compound selected from the group consisting of cage silane compounds A method for producing a germanium atom-containing higher order silane compound, characterized in that a germanium atom-containing higher order silane compound is produced by irradiation with light having a longer wavelength. The germanium compound is represented by the following formula (4)
R _x GeH _4-x (4)
Where R is a monovalent hydrocarbon group and x is an integer from 0 to 4,
Or the following formula (5)
(R _y GeH _3-y ) ₂ (5)
Here, the definition of R is the same as in formula (4) and y is an integer of 0-3.
The method of claim 1 represented by: A method for forming a germanium-containing silicon film, comprising: a step of applying a solution containing a germanium atom-containing higher order silane compound obtained by the method according to claim 1 to a substrate; and a step of heat-treating the coated substrate. . Following formula (1)
Si _i H _{2i + 2} (1)
(Where i is an integer of 2 to 10), a chain silane compound represented by the following formula (2) or (2 ′)
Si _j H _2j (2)
Si _j H _2j-2 (2 ')
(Where j is an integer of 3 to 10) and the cyclic silane compound represented by the following formula (3)
Si _k H _k (3)
(Here, k is 6, 8, or 10) At least one liquid photopolymerizable silane compound selected from the group consisting of cage-like silane compounds is irradiated with light having a wavelength longer than 300 nm. The method comprises a step of preparing a solution containing a high-order silane compound and a germanium compound represented by the formula (4) or (5), a step of applying the solution to a substrate, and a step of heat-treating the coated substrate. A method for forming a germanium-containing silicon film characterized by the above.